Bureau agents will gather evidence to ensure that criminal prosecutions of alleged terrorists are an option. The move is a reversal of the Bush administration's emphasis on covert CIA actions.

Richard Clarke, a senior counter-terrorism official in the Clinton and George W. Bush administrations, said the turnabout was long overdue.

"We have to return to the practice that we had before of arresting terrorists and putting them on trial," said Clarke, who added that the country's ability to do that "has atrophied."

CIA spokesman Paul Gimigliano said the agency would continue to play a central role in interrogations and counter-terrorism operations -- using techniques approved by the U.S. Army Field Manual-- in conjunction with other U.S. agencies.

Behind the scenes, some intelligence officials are resisting a broader criminal justice role overseas for the FBI, contending that it could inhibit the flow of intelligence if their own agents, or foreign governments, believe top-secret sources and methods might be disclosed during criminal prosecutions.

Two senior U.S. officials said efforts are being made to ensure that intelligence-gathering and law enforcement efforts proceed side by side. They stressed that the CIA and military would continue to play pivotal roles, particularly in gaining strategic intelligence against terrorist groups and thwarting future attacks.